Lesley Stahl has been a “60 Minutes” correspondent for 25 years. During her long journalism career she has covered Watergate, traveled to Rwanda to see Dian Fossey’s mountain gorillas, and interviewed Facebook founder Mark Zuckerberg.

Now, at 74, she’s turned her attention to a subject newly dear to her: becoming a grandmother to two granddaughters, ages 5 and 2, who call her “Lolly.” The girls are the children of Stahl’s only child, daughter Taylor.

Stahl’s new book, “Becoming Grandma: “The Joys and Science of the New Grandparenting” (Blue Rider Press, $27), is out this week. Newsday caught Stahl by phone in between her assignments.

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You say you felt a “staggering thunderbolt of joy” when your first granddaughter was born. How did that lead to a book?

I did have a thunderbolt of emotion. Everybody always told me being a grandmother is the best thing that can ever happen, but no one really explained the depth of feelings that go on inside you. So I decided to write the book to find out, Do all grandmothers have that, and if so, what is it? And then as I began to work on it, I realized there are all these other questions that branch off of it.

Such as?

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I was shocked — shocked — at how many grandmothers are denied access to their grandchildren. Not only did it surprise me, it hurt me. The grandmothers who spoke to me about it . . . they don’t understand why. The cruelty, from my perspective as a grandmother, the cruelty to deny a grandmother the thing that most of us care most about in the world, it’s almost unconscionable to me. The only thing that would conceivably justify it is if, as a parent, you believe the grandparent would hurt your child, but short of that it’s outrageous to me. As I kept digging and digging, I was coming up with categories of grandmothers who I didn’t know anything about.

You say this is the “age of the grandmother.” Why?

Probably because we’re so large in number, society is accepting us more and more in positions of authority. Look who is running for president.

You mention modern technology such as the obstetrician monitoring your daughter’s contractions from home on his iPhone, Skyping with your granddaughter while you were on assignment in Italy and playing with the Cookie Doodle app to “make cookies.” Which technology surprised you most?

If you live in a different city the fact that you can still be in their lives, even if it’s virtual, it’s changed the way we relate to our grandchildren. This way you can talk to your grandchildren, if you want, every day. And not only talk to them, you can see them. They can see you while you’re talking to them. I think it’s enhanced our involvement with them.

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You call any grandchild’s mother the gatekeeper to access and talk about how modern grandparents have to resist giving advice. Can you elaborate?

I think that most grandmothers find instinctively that the mother — their child or their daughter-in-law — is holding a kind of a power card that they didn’t hold up until the moment that baby is born. If we’re smart, we’re going to hold our tongue. If we’re not smart we’re going to be punished for it.

In the chapter entailing the competition between maternal and paternal grandmothers to be the most liked, you bravely asked your daughter’s mother-in-law about your relationship with her. What was that like?

She was so breathtakingly candid with me. Wow. First I asked her if she thought it was easier to be the mother of the mother, the maternal grandmother. She said, “Yes,” and I asked why. And then, boy, she was so open about it. And then I said, “Do you resent me?” There was this long, long pause, and then she said, “Yes.” That was the most difficult interview I did. As more than one psychologist said to me, it’s incumbent on the mother-in-law to make the accommodations.

Didn’t you feel that thunderbolt of emotion when your daughter was born? What is the difference between what you felt then versus when your first granddaughter was born?

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I think when you’re a parent the love is overwhelming, and it’s full and rich. But you also have responsibility, and you’re worried. I learned a lot about biochemistry, and there are all these hormones that new mothers have coursing through them, one of which makes them highly vigilant. We don’t have those worries. We have this . . . complete total loving without worries.

Untempered joy?

Untempered, unfettered, pure, complete, enormous, thunderbolt-y. And it lasts. At least it lasts for me.